Document EP 1 478 055 A1 describes a contact blade basket or skirt of an electrical plug connector, whose contact blades comprise at least two arc-shaped portions with opposed curvature. In simple terms, a contact blade with three arc-shaped portions is generated, of which the outer two portions—when viewed from the inside of the contact blade skirt—are convex, while the centre portion is concave. When the plug is inserted into the contact blade skirt, it contacts the two outer portions so that the contact blades are radially deflected.
In DE 10 2005 017 988 B3 an electrical contact socket is described which has a plurality of elongated spring elements for electrically contact making of a plug element and an outer contact socket which surrounds the contact socket. The spring elements which are elongated in the axial longitudinal direction comprise at least two tapering portions which are arranged spaced in the axial longitudinal direction for multi-point contact making of a plug element inserted into it. In addition, they have at least two consecutive expansion portions which are spaced in the axial longitudinal direction for multi-point contact making of an outer contact socket. The expansion portions are curved convexly, while the tapering portions are curved concavely.